A pigment, as related to its use in concrete, mortar and cement paste is defined as a fine dry powder, dry granules, aqueous suspension, or slurry, of the powder or granules, insoluble and inert to the concrete ingredients and which imparts a specific color to the product. The color of a pigment can be described in terms of three properties: hue, value, and chroma, which are indicative of the purity (oxide content) and the brightness of the pigment.
Pigments in the dry form exist as agglomerates of particles. The ease with which the aggregates are broken down and dispersed in concrete, mortar and cement paste depends on the extent to which the forces of attraction between the particles is reduced. The coloring action of pigments is dependent on the extent of smearing over the cement and fine aggregate in the mix. Therefore, cement and fine aggregate contents will significantly influence the degree of coloration achieved.
Dosages of pigments typically decrease slump, increase the water demand and premature stiffening of the cementitious composition and may produce flash setting. To increase the slump of the cementitious mixture additional water is added, however, in general the higher the water content of the mix, the lighter will be the final color. The increased water content also decreases the strength of the resulting cementitious composition.
Therefore, it is desirable to provide a colored cementitious composition comprising a liquid coloring suspension which contains a dispersant and a pigment that improves the color, increases or has no effect on slump, and lowers or has no effect on the water demand of the cementitious composition. Therefore, a liquid coloring suspension which improves the color of cementitious compositions without increasing the water content or decreasing slump would be advantageous in the industry.
U.S. Pat. No. 5,853,476 to Will discloses a method for coloring cementitious systems using compacted inorganic granules, wherein the compacted inorganic granules comprise an inorganic pigment and a non-polycarboxylate dispersing agent.
U.S. Pat. No. 4,514,947 to Grail discloses a roof tile made of a composition of matter comprising cement, silica sand, iron oxide pigment, acrylic polymer resin, an antifoaming agent and water and formed into a shape.
U.S. Pat. No. 4,714,781 to De Witte discloses iron oxide slurries and suspensions that are made from water, iron oxide pigments and a non-polycarboxylate dispersing agents such as water soluble salts of citric acid and tartaric acid.